Valve



Patented May 18, 1937 U-Nrrsn` STATE-s PAI-E lorries; l AMMZ''gI 418Claims.

This invention relates -tofluid controlvalves using oil as a` powerfluid) employeditoeffect motions 'ofmachine elements, andthe-'principalobject of 'thisiinvention is to provide-a valve unit that will performthe functionl'o'f a`-relief-valve and at lthefsame timeserve-to`displacethe function `of Va pressure 1gage in-suchhydraulic circuits; tHydraulic circuits-nowgin general use,` employ a' relief valveto allowthe passi-ng ofthe-'fluid when a ygiven pressureA is reached Sand'ordinarily use a separate pressure Vgage 'toindicatethe -pressuredeveloped; In-many installations itis" only necessary toknow thepressure which thefluid attains when `bypassing through; the reliefvalve` to assure satisfactoryjoperation of 'the `mechanism and safetytotheoperator. Usually'relief valves area-made adjustable togive'awide'variaj tion of vrelief pressures,'and the operatoradjusts therelief `pressures to a specified'A limit -assshowni by'thepressure'gage;Those familiar with this artA will recognize 'the' weakness`offplacing'this adjustment inthe hands'of an operator v'who'may easilyset this pressure toohigh or too'lowfor D satisfactory operationV ofthe-mechanism; or 'for his own safety. Inthe'electrical industry;Y thecorresponding weaknessj-is offset bythe-use ofinterchangeable fuses(whichA functionforfthe safety of theelectrical 'circuit as the j reliefvalve does for the" hydraulic circuit) having definite ratings andwhichare `notadjustable'in*most industrial applications, and thereforetheloperator can not convenientlyadjust 'same 'tojjeopardize the'successof the installation; Similarlyg'my valve is designed for-hydraulicapplications withE a definite range of relief pressures that are `onlypermissible for `the particular" installation; and this rating cannot-beVexceeded or altered by 'the operator without replacingr ther spring'cartridge in somewhatthe same man-ner asan'e1e`ctricianwould replacelan "electrical fuse.

A`further object of this invention' isto pro-4 vide arelief valve witha. built-in interchange-V able spring cartridgethat will give afrangevof relief pressures that 'are permissibleordesired for satisfactoryoperation'of fluidcircuits;

Another object ',of this invention lvis vto provide a valve' that willcause Luid such as loil'tohypass through itat a higher,pressurewhen theoil is cold than when the oil becomes heated. This characteristic isintended vfor those hydraulic applications that start up sluggishlywhenv the oil isrcold due to a greater resistance to the flow oftheeiland vtoa greater frictional (Cl.l IS7-P153).

resistance-` off moving: parts atsuch time.'v By supplying-oil.l itolthe mechanismv :with fa 1 slightly higher pressurefduring thefstart Yup.periodf'this sluggis'hness fof: operatiom can; be compensated for. Thisfeaturey is attained 'byzusinga longe narrow slot in-l the relieff-piston instead*` ofi the curved VA oriiice;l Asagiven` volume-.off`cold oil will force therelieflpistonftoaIposition that will. give-va'larger fexhaust xport l than will.;the .same volumev of Vheated 'L oiland thus s compress?. the spring to a -higher pressure,thereforeftheivcold oil .will be bypassed r at .iashigherzpressureY thanwill the heated oil; The narrowfslotvaccentuates this amount :of fextraApiston traveliirequired Ifo'r a given change in exhaustiport'sizerequired..

The widthlofsthe-slot or the:spring-characteristic canl be altered `Ito:givethe required `ris'ev in pressureneededto overcomeathe sluggishn'essof ini' tial.; machine fmovements during. .'thestart `lupf period.

Another object of this vinvention issto. provide al: relief 'valve 5that Iindicates when and rat 1 .what

pressuresfluidlis-ibeingbypassed. A still further. obect-o-f'thiszinventionkis' to utilize a-'springl' thatri's rlarger outside coillldi`ameter than theval-ve-v pistonjto-gainfthedecided advantage of amoreresilient spring characteris'tic. Thus throughfthefuse of tliis more'resillier'it' springvythe 'relieving pressurewat the time-'the exhaustport fopensrfforf'initial bypassing-can 'be made; to Ed-iir .lessv fromthe.Epressureattained. when the orifice is -ropened ithef amountrequired fortheiavaiilable Voluniefofidischarge. e Y

'Other minor objects of `the invention willibe hereinafter set fforth.'1- f I `will explain the invention withreferenceto the accompanyingdrawing, which illustrates severalv practical embodimentsthereof, toenable others l:familiar 'rwithif they art toffadopt and use the same;andf will summarizeY inthe zclaims -the essential featuresofftheinvention, theyno'vel features of construction,` and novel combinationsof parts vforwliichl protection is l desired.' In said drawing: Figfflis-a longitudinalsection through-one embodimentof "my valveutilizinganon-adjust# able Ispring cartridge. l' y Fig. 2 isY a fragmentary"longitudinal section showing the -pistonL infthe position it assumesvinv the" casing when -iiuidis being `bypassed through the orifice. IFig. 3 is a transverse section through ,the exhaust port on the line3L3, Fig. 1 `,l showing a'convenient method of drillingto formthelneceslsary discharge Vopenings for the flowof riiuid CII when thepiston has been moved into bypassing position.

Fig. 4 is an elevation of the interchangeable non-adjustable springcartridge of the type used in Fig. 1.

Fig. 5 is a fragmentary longitudinal section showing the shape of theorifice in the piston used when higher relief pressures are requiredwhile certain fluids are cold than when these uids are heated.

Fig. 6 is a longitudinal section illustrating a modication of the valvehaving an adjustable spring cartridge and having a calibratedV rodadjustably connected to the valve piston, and showing the piston in theposition assumed when a moderate amount of fluid is being bypassedthrough the orifice opening, the calibrated rod being' shown in positionindicating a medium pressure.

Fig. 7 is an elevation of the piston and calibrated rod in theirrespective positions assumed in the valve shown in Fig. 6 when a lowdelivery of fluid is being bypassed ata medium pressure, the amount ofopening of the orice being observed by reference to the line A-A of theexhaust port, and the position ofthe calibrations on the rod beingobserved by reference to the line B B of the end of the valve cap.

Fig. 8 is an elevation of the piston and calibrated rod in theirrespective positions assumed in the valve (Fig. 6) when a high deliveryof fluid is being bypassed at a medium pressure.

Fig. 9 is an elevation of the' piston and calibrated rod in theirrespective positions assumed in the valve (Fig. 6) when a mediumdelivery of iluid is being bypassed at a higher pressure; and

Fig. 10 is an elevation of the piston and calibrated rod in theirrespective positions assumed in the valve (Fig. 6) ,when a mediumdelivery of fluid is being bypassed at a lower pressure.

Referring to the Figs. 1 4, IB designates the cylindrical valve bodyhaving a closed end Illa, and II the valve end cap connected by screwsI2 extending through the body` oiset from the axis thereof, said screwsentering tapped bores Illb in the closed end of the body. Gaskets I3under the heads of screws I2,` and gasket I4 under the cap |I` sealthespring chamber ofthe valve against leakage. Within an axial bore I0cinthe end Illa. is a valve piston I5 which is splined as at I6 toprevent rotation, said piston having a substantially curved V-shapedorifice opening I5a in its outer end for the purpose hereinafterdescribed, and having an enlarged head I5b on its inner end adapted tocontact with the spring cartridge unit. `Co-axial with bore IUc is atubular extension Id threaded as at I1 for connection with a pipe (notshown) introducing fluid under pressure into the valve. In Fig. 3 Athedischarge ports are shown, same consisting of a pair of parallelvertical bores Ille disposed transversely of the bore Illc andregistering therewith, the upper ends of the bores being closed bycaps 9threaded thereinto. The lower ends of` bores Ie register with adischarge portlllf tapped as at 20 for the reception of an exhaust pipe(not shown) of the system or circuit. Fluid under; pressure enters inletInd and passes through the exhaust orifice |5a when the piston I5 is,retracted as in Fig. 2 and then passes into the discharge ducts Ie andout through port If.

'I'he spring cartridge, shown in Figs. 1 and 4, controls the movement ofpiston I5, same comprising a spring 2|, plate 22, spacer 23, screw 24,identifying plate 26, and the end cap I I. The plate 22 is somewhatsmaller than the chamber |0 and is provided with openings for the screwsI2, the plate 22 freely sliding thereon. At the center of plate 22 is atubular extension 22a closed at its outer end; and the screw 24 passesthrough the end of the extension 22a and into a tapped bore I Ia in thecap I I to connect the plate 22 to the cap. The spring 2| is of slightlysmaller diameter than body I0 and is interposed between the plate 22 andcap II, same enveloping the screws I2. If desired a spacer washer 23 maybe used between the spring 2| and cap I| to modify the characteristicsof the spring. Plate 22 contacts the end |5b of piston I5.

A duct 25 through the end member Illa connects the spring chamber withthe exhaust ducts Ille, allowing flow of iluid into or out of the springchamber. 'Ihe pressure in the spring chamber will never appreciablyexceed the eX- haust pressure. Thus gaskets I3 and I4 are required toseal against the exhaust pressure only. The identifying-plate 26 isattached to end cap II and serves to identify both the flowcharacteristics as well as the relief pressure range of the particularvalve.

The spring 2| is made with a relatively large coil diameter so that thevariation in spring force obtained from that position of the piston thatallows only a small orifice opening.. to that spring force obtained fromthat position of the piston that allows a full oriiice opening, will besmall. Thus the resulting hydraulic relief pressure range will be heldbetween sufliciently narrow limits from the time that fluid starts tobypass to the time that the full available volume is bypassing, to makethis relief valve satisfactory to many applications. This feature in myvalve of bypassing uid at only a small variation in relief pressures fora wide variation in exhaust port openings, functions also to prevent thebypassing of fluid that could be advantageously used in power circuitsuntil a pressure is attained that is very close to the necessary reliefpressures for that volume of discharge.

A small Variation in spring force and resulting variation in hydraulicpressure for changes in discharge orifice openings are unavoidable withthe spring placed in a non-adjustable cartridge as shown in Figs. 1 and4. The choice of the spring is a vital factor in obtaining asufficiently small variation in relief pressures and yet keeping thedimensions of the valve to that which is commercially acceptable. Aspring made large in coil diameter will be considerably shorter in solidlength, than a spring held to an outside diameter which is less than thepiston diameter, when the two springs have the same load variation foran equal amount of deflection. In fact, the spring with the smalloutside diameter will be so long in solid length that the resultinglength of the enclosing valve housing would be inconveniently long forcommercial applications. Thus there is a great saving in length of thevalve unit effected by making the outside diameter of the spring coil 2|larger than the diameter of the valve piston `I5 when the desirablespring characteristic of a small change in pressure is desired forvarying exhaust orifice openings. The gain in diameter of the Valvehousing resulting from the use of the spring with its larger coildiameter is not detrimental to the commercial acceptability of thevalve, since the drill depth of duct Illf required for the thread tapclearance of this duct determines the radius of that por- 4tion-of :the:Valve body-sand" asthis valvefisz'mounted-byrscrewingit onato theintakeductill lld'pthis x radius*l canzfbeataken. asl the ,radius "of ther4entire body Without erequiring additional `:mounting 5 clearance.

1 suciently. long'ttor;allovwforaantincrease*,:inithe amount of pistonmotiomfandvismadetrelatively :narrow soithat ar considerable end motion,ofi the piston 'l will ,beil required "for .aagigiven :.arruruntf :ofchange/in :exhaust foriceopeningintoducts i 0e. An vincrease-iin oriceopening'nwillbeneededtfor ycoldzzliquidsuchaas oil, owingaat'agivenTrate through the valve; over.- thatV` orificetopeningnthat l5will-,berequiredawhenthezsame volume is'iflowing after thevoil 'hasbeenheated ;;.'lhus,;y :since: the :spring 2 l1 is kcompressed:moreswheniv thexcoldoil is flowing;V thezpressurefatwhichtheifluidfwill albe' bypassedawill beagrea-ter. `:'Ilhexefect, ofthis',a-"hydraulic'rne'chanism that operatesfmore slow- -ly when irststartedtup. ".'Ihis sluggishness offa hydraulic .mechanism-iduringf-.thestartf.:v.upzzpe riod.;is;.dueA 'largely toi thegreater i"restrictionAaof 251 themow: of .cold-oil through its ducts =and ports fand' ,toga-1gre'aternmechanical` friction-of.A Amoving parts lubricated with colderlubricating :poilaat thisgtime. 'When :higheri` pressures nare suppliedto hydraulic mechanisms 'irrmost"cases,` theyibp- 30; eratefvmorerapidly:because additional pressure "is ilgopenings encountered :Linithezauseof the f; valve shown in Fig. 1 are too great foreaparti'cular hydraulic,circuit .Thisi modicationr- .-hasf'v the addition'of an.. externallyadj ustable' rod. 30. slidably mounted ini thefendcapiS l andthefzpacking '132. .This rod vis calibratedas at30al1andiadjust ablythreaded onto fthe end.l of:v a rmodied. piston valve i 33. iAnwinterchangeable spring. cartridge is alsoelused". which,\.asshown:in' Figxl; consists zof the calibrated rod30;.:endcap'3l11withpacking32, plate 35, spacing washer 23, identifyingiplate SZB, andcross pin'31.lThese'partsare assembled ftogether iny a selfcontainedunit'beforeirbeing .':mounted :inl the body l0. hGasket' iIll runder.end vean-3 l'. and gaskets. under Ythe heads "fof screws' l 2 (not shownin' Fig; 6)'seal 'the springicasingff-rom leakage. `The screws I2 areshown Biand -hold .the end cap 3| -in'zplaceinthevsamezmanner .as thesescrews hold'endcap l lin place inEig. 1. .The cartridge Atype ofconstructionespecially fa- 65, cilitates :assembly of .these partsbecause the spring itself must be compressed a considerable r amountbeforerit can' be=assemb1edrintofthe cartridge. The spring spacer f 23serves- Atoamake ,mi small changes in spring pressure:and-isalsofused to`correct small unavoidable pressu-reyariations that are the result YVofsmall Adimensional.errors of the spring :occasioned during itsmanufacture. The identifying plate v2li serves to mark thenpar- Yticular cartridge and .to inform theoperatorfof 1.,.thef.;pressuresanddisplacement; characteristics: of thissparmcularrcartridge; andl valve.ZDuctl'llllnis 'sta ilealcreturm'f-.or the'punposetbt conyeyingiawayiranyjopo'ssibleffileakagerzlrhm:the packing1i32 i; and`@preventing.thissleakage fromtseeping;- aout.. around 5fl6.tozipreyenterotation Spring pla-tex 35fis pre-\fVentedironr'rotatiombythefftwoscrews I Zzshown :frinfFigt'fSupon=whichit isrs'lidablymounted; 'iCali- --;brated1rodt3llithasf'arts.annularishoulder .3011: rol0 tatably journal'edin plate 35.Rodz30xisvtapped tot' receiveathefthrea'dd end'z33afi ori-:pistoni 33.

'llhenninfimum` zlimit f.` availablerelief; pressure`Liseobtainedrivilfhen the#v endofrpistonf-BB#engages 'f the-eend.oftshoulderei'llllrhf rod-V30. *Theimaxif l5 :mum xlimitcof .-pressureiis @obtained -Vwhen the tthreadedi endifaiiofffpiston'33:riiszfunscrewed en- 'ttirely-:otfoftthe tappd1bore .inf 'rod 1*'30.i When =;thei threadedeencleof ffpiston `533 l is entirely'1unt-threaded.iromrodzilw thefkeyL pin i6 is caused to" 20 #engagesblieeinnerfend yofiitsfkeyway,` and' rod-13D Ytogether withftheiplate35`isr causedto movel end- 1 wlse'aagainstthe springfor.L afshortdistance; but nnot enough tofsexpose any'V calibration lon rodrll.'WVhen `rod 30 fisssubsequently@rotated to -screw"25 samef'zontot-he'fthreaded' en'dz: 'offfpistonf- 3 3 '-itf will ifbeiuder `springpressure to'reeengage the threads so that `thealadjustablel connectionbetween '.piston eSSSiandrod'a-willibefref-established.

i 'lhei-maximun'andwminimum Vrelief valve pres-V 30 n `suressettings,.foutlinediabovefplace -only aparvzticular:range .Tof-pressuret'settings at the fdis- -ifposal oKitheoperator` andthusfpr'event'ihimf'from i .adjustingi'thejlpressure'lftoo :high:'orfztoo fslow Afor satisfactory operation of the mechanism -or-'for 35.this 'own` safety. 4:A'valveffitted Withaspring that restricts 'thefrangeif: frelief .f pressures to withinrnarrew7limits,:.-:alsoitunctions-. to :preventany -vabyvpassing lith-roughfthe valve l until .'f a vpres'sure fwhichrisfveryf close.-ftothefirelief pressure.' is at 40 atainedzat fthe iirleteport llld.

The-:calibrationsUa'ioni'the -ro dfi 3 D; as this rod isfnnoved toaexposelthem: to viewgfindicatethe presslneiat` which."thelfluidfis!being.' bypassed. These calibrations are placed in anylsuitablefiumarmen-mand fmayrbegstamped t or.iotheryiisel la-.ebeledl-vdtlrtheipropemnotations. -Itwillbe'lnotedisthatf-when,thefpressureeonthis yalvefisflessfthan'`athat.twl'lich1sfirequired';to? cause ericlivisefl motion toncthistrodiDithat'rotational adjustment-fof .this '#50 rodfwill:vv-notifrnmreiiit-endvllise 2 renough to #expose.tanynalibraftions*iThusiavisualtindicationrof the .'settingrA ofth-is@Halve i 'cani ionly tbeifmadef while ftheuidsiso'eingebypassed.xAccuratei'fsetting. of :.xthe'relief pressureris wmadeawhile thefbypassing. of i '55 fvfthat-yolume .ofaluidris taking place forlwhich.the .elpanticu-larissettingrisdesired. .muysettingLwithifintheirangelfof this l-fxzalve,ithat'iis,"within therrange'lof the c brationsfoi thistrodeanlbe-made at :this time. ".Ihefrange rfof settings l.fis tid'eter- 2 60 minedslay-'1itheerrangeil -'ofaspring forces developed 'by ithe r spring? -for aany articular springcartridge,. and to alterthisfrangeof-availablei-setv tings;-the-cartridge':mustl lbe removed andl either iurdergoealteration "Tof`theifspring 2| .or-spring 65 fl spacer?? 3: orf elseifber-replacedtibyi anotherV inter- `changeablespring cartridge"fhaving the desired`range"oftpressure'fsettirigs.

l*ArrA 'allowance for'rthelpos'siblef rates vof'iiowi as-"-Wel1'aas=-.anallowancelior the possible diierences 70 "in viscosity`andf'other .characteristics of the uid, Twill require:` axwidefrangeiof-.exhaust i orifice' openfin'gs.zfnrFig.:'Gthisi'oniceopening"'at lia is shown approximately half :openand it is considi'zeredfthatv, afmedium' amount :of -luidr/Would pass;75

through this opening with the piston 33 in the position shown. Theadjustments built into this valve permit adjusting the relief pressureto the full range of pressures as indicated -b-y the calibrations on therod for any particular exhaust orifice opening from the smallest opening4| (Fig. '7) to the largest opening 42 (Fig. 8). The operator canreadily make these adjustments by rotating rod 30, but the operator canonly adjust to the limits of the particular spring cartridge used.

Fig. 7 shows piston 33 and calibrated rod 30 in their respectivepositions that they would assume in Fig. 6, when a small volume of flowis taking place at a medium pressure. Orifice 4| is nearly closed androd 3U is half way out as noted by referring to the reference lines A-Aand B-B drawn from Fig. 6. Fig. 8 shows orice 42 opened to a fullopening and yet the relief pressure is the same as in the above Fig. 6.Also Figs. 9 and 10 show the exhaust orifice open to vpermit a medium.flow but in Fig. 9 the relief pressure is set at a high valueand in Fig.10 the relief pressure is set at a low value. Thus Figs. 6, 7, 8, 9and10 show five of the possible positions the piston 33 and calibrated rod30 could takein the assembly shown in Fig. 6, and these positions areindicative that a full range of relief pressures that are built into thespringk cartridge for this valve are available for any size of exhaustport opening that can be gained by the full range of positions of thepiston.A It will be noted that calibrated rod 30 indicates-when and atwhatr pressure fluid is being bypassed by this valve.

While several particular embodiments of the invention have beendescribed, its application is intended to cover any variations, uses, oradaptations including such departures from the present disclosure ascome within known or customary practice in the hydraulic art, and as maybe applied to the essential features hereinbefore set forth and as fallwithin the scope of the invention or the limits of the applied claims.

I claim:

1. In a valve for controlling the relief pressure of fluid in a fluidcircuit, a casing having a spring chamber and having inlet and exhaustports adapted to be connected in the circuit; a slidable valve in thecasing between the ports adapted to be operated by fluid pressure at theinlet port and extending into the spring chamber, and a removableself-contained spring cartridge including a spring of predeterminedcharacteristics in the spring chamber opposing movement of the valve,said spring cartridge comprising a fixed plate; a movable plate slidablymounted on the fixed plate and adapted to enter the spring chamber andabut against the valve; and said spring being of relatively largediameter and interposed between the movable and xed plates; and meansfor removably securing the cartridge within the spring chamber.

2. In a valve for controlling the relief pressure of fluid in a fluidcircuit, a casing having a spring chamber and having inlet and exhaustports adapted to be connected in the circuit; a slidable valve in thecasing between the ports adapted to be operated by fluid pressure at theinlet port and extending into the spring chamber, and a removableself-contained spring cartridge including a spring of predeterminedcharacteristics in the spring chamber opposing movement of the valve,said spring chamber being open at one end; and said spring cartridgecomprising an end having a spring chamber and having inlet and exhaustports adapted to be connected in the circuit; a slidable valve in thecasing between the ports adapted to be operated by the fluid pressure atthe inlet port and extending into the spring chamber; said valve havinga notch in its end adjacent the inlet port forming an exhaust portorifice; a removable spring cartridge including a spring ofpredetermined characteristics in the spring chamber opposing movement ofthe valve; and means for externally adjusting the relief pressureswithin the available range of the spring characteristics irrespective ofthe amount of fluid flowing through the valve.

4. In a valve as set forth in claim 3, means for equalizing pressures inthe spring chamber and exhaust port.

5. In a valve as set forth in claim 3, said spring being of largerdiameter than the valve to provide maximum resiliency and to cause delayin movement of the valve until a pressure approximately that of themaximum relief pressure is obtained at the inlet port.

6. In a valve as set forth in claim 3, said spring cartridge including amovable member cooperatr ing with the spring for altering the springtension and the magnitude of the relief pressures.

7. In a valve as set forth in claim 3, said notch being of substantiallycurved V-shape.

8. In' a valve as set forth in claim 3, said notch being'relatively longand narrow whereby the piston must move a relatively great amount for agiven orifice area change to increase the relief pressure for cold fluidas compared with the relief pressure obtained from the same flow ofheated fluid.

9. In a valve as set forth in claim 3, said spring cartridge comprisinga ilxed plate; a movable plate slidably mounted on the fixed plate andadapted to enter the spring chamber and abut against the valve; and saidspring being of relatively large diameter and interposed between themovable and ilxed plates; and means for removably securing the cartridgewithin the spring chamber.

l0. In a valve as set forth in claim 3, said spring chamber being openat one end, and said spring cartridge comprising an end plate adapted toclose the open end of the spring chamber; a movable plate slidablymounted on the end plate and adapted to enter the spring chamber andabut against the valve; and said spring being of relatively largediameter and interposed between the movable and end plates; and meansfor removably securing the cartridge within the spring chamber.

11. In a valve as set forth in claim 3, said valve being non-rotatable;and said adjusting means comprising a rotatable rod carried by thespring cartridge and adapted to move endwise as the spring iscompressed; said rod extending through the cartridge, and having athreaded engagement with the valve, whereby rotation of the rod willadjust the valve with respect to the` exhaust port to variT the exhaustorice area for any given relief pressure.

12. In a valve as set forth in claim 3, said valve being non-rotatable;and said adjusting means comprising a rotatable rod carried by thespring cartridge and adapted to move endwise as the spring iscompressed; said rod extending through the cartridge and having athreaded engagement with the valve, whereby rotation of the rod willadjust the valve with respect to the exhaust port to vary the exhaustorifice area for a given relief pressure; the extending portion of saidrod being calibrated whereby endwise movement thereof will indicate therelief pressure at which flow of fluid takes place.

13. A valve for controlling the relief pressure of uid in a fluidcircuit, comprising a casing having a spring chamber and having inletand exhaust ,ports ad-apted to be connected in,y the circuit; a slidablevalve in the casing between the ports adapted to be operated by thepressure of fluid at the inlet port and extending into the springchamber; said valve having a notch in its end vadjacent the inlet portforming an exhaust port orice; a removable spring cartridge including aspring of predetermined characteristics in the spring chamber opposingmovement of the valve; means for externally adjusting the reliefpressures within the available range of the spring characteristicsirrespective of the amount of fluid flow through the valve; and meansfor visually indicating at what pressure flow of fluid takes place inthe valve.

14. In a valve as set forth in claim 13, said valve being non-rotatable;and said adjusting means comprising a rotatable rod carried by thespring cartridge and adapted to move endwise as the spring iscompressed; said rod extending through the cartridge and having athreaded engagement with the valve, whereby rotation of the rod willadjust the valve with respect to the exhaust port to vary the exhaustorifice area for a given relief pressure; and said visually indicatingmeans comprising calibrations on the extended portion of said rodwhereby endwise movement thereof will indicate the. relief pressure atwhich flow of fluid takes place.

15. In a valve for controlling relief pressures in a fluid circuit, acasing having inlet and exhaust ports adapted to be connected inthecircuit; a slidable valve in the casing between the ports adapted to beo-perated by fluid pressure at the inlet port; said valve having a notchin its end adjacent the inlet port forming an exhaust port oriiice;spring means opposing movement of the valve; said exhaust portscomprising a pair of parallel bores entering the casingztransversely ofthe valve and disposed on` opposite sides thereof, said bores eachcommunicating with an opposite end of the notch when the Valve isopened.

16. In a valve for controlling relief pressures in a fluid circuit,acasing having inlet and exhaust ports adapted to be connected in thecircuit; a slidable valve in the casing between the ports adapted to beoperated by fluid pressure at the inlet port; spring means opposingmovement of the valve; said exhaust ports comprising a pair of parallelbores entering one side of the casing transversely of the valve anddisposed on opposite sides thereof, said bores communicating with theinlet portion when the valve is opened; the lower ends of the borescommunieating with a single outlet; and members closing the open ends ofthe pair of bores.

17. In a valve for controlling the relief pressure of fluid in a fluidcircuit, a casing having a spring chamber and having inlet and exhaustports adapted to be connected in the circuit: a slidable `valve in thecasing between the ports adapted to be operated by fluid pressure at theinlet port and extending into the spring chamber, and a removableself-contained spring cartridge including a spring of predeterminedcharacteristics in the spring chamber opposing movement of the valve,and members extending through the cartridge within the coils of thespring and entering the casing, for securing the cartridge in positionin the casing.

18. In a valve for controlling the relief pressure of fluid in a fluidcircuit, a casing having a spring chamber and having inlet and exhaustports adapted to be connected in the circuit; a slidable valve in thecasing between the ports adapted to be operated by fluid pressure at theinlet port and extending into the spring chamber, and a. removableself-contained spring cartridge including a spring of predeterminedcharacteristics in the spring chamber opposing movement of the valve,said spring chamber being open at one end; and said spring cartridgecom'- prising an end plate adapted to close the open end of the springchamber; a movable plate slidably mounted on the end plate and adaptedto enter the spring chamber and abut against the Valve; and said springbeing of relatively large diameter and interposed between the movableand end plates; and members extending through the end and movable plateswithin, the coils of the spring and entering the casing for securing thecartridge in position in the casing.

ROBERT s. CoNDoN.

